8. BOOST ADJUSTMENT.
The best way to go is to have an electric
solenoid under the bonnet controlled by a switch inside the cabin in an out of the way
place where parking attendants will not notice it.( or your mother in law) The
electric 12VDC solenoid
can be any type virtually as long as it can be mounted and plumbed easily and is really
just an electrically operated air valve or tap that is normally OFF or CLOSED with no
power applied.
As most waste gates are controlled as explained previously, the way to fool the waste gate
into not opening and reducing the build up of boost over the usual level is to not allow
the true boost level signal to get to the waste gate canister. This is achieved by cutting
the pressure line pipe ( usually a tube of rubber covered with heat resistant material) in
the center and inserting a 'T' fitting of metal tube preferably to withstand the heat in
this area.
The free end is now connected by more tube
to one side of the solenoid and on the other side a small variable tap is affixed. The
reason for the small tap is to adjust the amount of air bleed when the solenoid is
switched on to increase the boost to your preferred set level. (probably just below the
fuel cut off pressure for your vehicle.) This now gives your normal or low level of boost,
and high boost set at your preferred preset level. This is the safest and most practical
method of modifying and controlling boost for more power on most turbo vehicles that I am
aware of.
Any input from owners on this subject or any other for that matter is welcomed even if you
don't agree with me!
8.a EXHAUST
Not mentioned previously is the fact that a more efficient exhaust system will immediately
increase your boost from standard by a considerable amount. One of the first modifications
that I made was to check around the suburbs for an exhaust Workshop that could handle
large diameter mandrel bends for the ultimate system.
I figured if I was going to do it, I might as well do it properly (read BIG) This was
especially after I found that Mitsubishi wanted over $300 for a rear muffler that needed
replacement. I eventually found a truck specialist that could make and fit a full three
inch system from the back of the turbo to the custom straight through rear muffler.
Bonus!! they also did audio testing for road worthy's so it complied with the letter of
the law. (JUST!!) Also it only cost fifty dollars more than the MIT's muffler all up so it
was an absolute bargain. (even in 1987) I could not believe it when I carefully drove down
the drive and onto Ballaraat road and then floored it!
The boost gauge wrapped around to the end, and the fuel cut-out cut in.
WHAM BANG COUGH, GULP!
That was even after I had previously wound the boost back down ( early days adjustment)
because I had expected it may go up a bit with the much more free flowing system.
Understatement!!
The only other time I have been surprised like that since I had readjusted it to a
reasonable (1.2 Bar) level was when out at the drags and disconnected the whole exhaust
from the back of the turbo down pipe.
Needless to say, I have burnt my fingers a few times trying to adjust the screw on the
waste gate arm before I built the electric solenoid. Just consider this for a moment, what
do you think happened at the drags with a radical change of no exhaust at all? You
probably guessed it, the noise was incredible, even more than the big V8's and everyone
looked, but then laughed when the engine detonated (as in lean mixture, not exploded thank
goodness) and I went slower than normal (14.5 sec) Of course I was moving a vast amount
more air through the engine but nowhere enough fuel to keep the mixture correct to make
power. Back then I was just starting to try to make sense of all this turbo
(free?) power.
You have to burn fuel to make power irrespective of engine size.
The moral of the story is if your serious about wanting your turbo to perform, you have to
help it to breath freely through at least a two and a half inch system (sorry I'm not
metrisized, too old!) from the back of the turbo itself.
